1. Field
The present invention relates to a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery comprising the same. More particularly, the present invention relates to a positive electrode for a rechargeable lithium battery that has good thermal safety and cycle-life at a high voltage.
2. Description of the Related Technology
A lithium rechargeable battery has recently drawn attention as a power source for small portable electronic devices. It uses an organic electrolyte solution and thereby has the discharge voltage twice as high as that a battery using an alkali aqueous solution, and accordingly has high energy density. For positive electrode active materials of a rechargeable lithium battery, lithium-transition element composite oxides being capable of intercalating lithium comprising LiCoO2, LiMn2O4, LiNiO2, LiNi1-xCoxO2 (0<x<1), LiMnO2 have been researched. As for a negative electrode active material of a rechargeable lithium battery, various carbon-based materials such as artificial and natural graphite and hard carbon have been used, which can all intercalate and deintercalate lithium ions. Graphite of the carbon-based material increases discharge voltages and energy density for a battery because it has a low discharge potential of −0.2V, compared to lithium. A battery using graphite as a negative electrode active material has a high average discharge potential of 3.6V and high energy density. Furthermore, graphite is comprehensively used among the aforementioned carbon-based materials since graphite provides better cycle life for a battery due to its outstanding reversibility. However, a graphite active material has a low density and consequently a low capacity in terms of energy density per unit volume when using the graphite as a negative electrode active material. Further, it involves some hazards such as explosion or combustion when a battery is misused or overcharged, because graphite is likely to react with an organic electrolyte at a high discharge voltage.